Electrical submersible pumps (ESP) are widely used to pump well fluid from hydrocarbon producing wells. A typical ESP includes a centrifugal pump driven by an electrical motor. A seal section or pressure equalizer normally connects between the pump and the motor to reduce a pressure differential between well fluid on the exterior of the ESP and motor lubricant in the motor. In addition to a pump, motor, and pressure equalizer, the ESP may include other modules, such as a gas separator or and additional tandem motor.
The modules of a typical ESP are connected by bolts that extend through external flanges at the upper and lower ends of each module. More recently, threaded connections between the various modules have been introduced. A threaded connection employs a rotatable collar with internal threads mounted to a neck. The collar engages external threads of an adapter of the adjacent module and bears against a shoulder ring. While threaded connections work well, improvements are desired.
For example, a threaded connection between a motor and a pressure equalizer and a threaded connection between a pressure equalizer and a pump would normally not involve electrical terminal connections as well. Connections between tandem motors do include electrical terminal connections, reducing available space for the components of a threaded connection. Prior art shoulder rings for threaded connections occupy a larger space than is readily available for connections between tandem motors.